The present invention relates to a non-azide based gas generating composition. The gas generating composition of the present invention is particularly useful for inflating an inflatable vehicle occupant protection device.
An inflator for inflating an inflatable vehicle occupant protection device, such as an air bag, contains a body of ignitable gas generating material. The inflator further includes an igniter. The igniter is actuated so as to ignite the body of gas generating material when the vehicle experiences a collision for which inflation of the air bag is desired to help protect a vehicle occupant. As the body of gas generating material burns, it generates a volume of inflation gas. The inflation gas is directed into the air bag to inflate the air bag. When the air bag is inflated, it expands into the vehicle occupant compartment and helps to protect the vehicle occupant.
Azide based gas generating compositions for generating gas to inflate an inflatable vehicle occupant protection device have the advantage that they produce non-toxic nitrogen gas during combustion and produce gas at relatively low gas temperatures. Non-azide based gas generating compositions, in contrast, typically produce gas at temperatures well above the temperature of gas produced by azide based gas generating compositions with some approaching 4000 K.
While non-azide based gas generating compositions potentially are thermodynamically efficient, they present heat management problems. For instance, it may be necessary, because of the high temperatures, to manufacture certain components of the vehicle occupant protection device of more expensive materials that are resistant to the high temperature gas which is generated. In addition, the non-azide based gas generating compositions tend to produce reaction products which may be in the vapor phase at high temperatures and thus more difficult to filter.
Various attempts to cool non-azide based gas generating compositions include adding chemical coolants to the compositions. Chemical coolants, however, tend to add to the volume of the gas generating material required without increasing the gas output. This reduces the gas output per volume of gas generating material in an amount dependent upon the amount of the coolant added.
The present invention is an apparatus comprising an inflatable vehicle occupant protection device and a gas generating composition that, when ignited, produces gas to inflate the inflatable vehicle occupant protection device. The gas generating composition comprises a non-azide nitrogen containing organic fuel, an inorganic salt oxidizer, and a metal organic coolant. The metal organic coolant is selected from the group consisting of alkali metal formates, alkaline earth metal formates, alkali metal oxalates, and alkaline earth metal oxalates. The amount of metal organic coolant in the gas generating composition is a cooling amount. A preferred non-azide nitrogen containing organic fuel is one selected from the group consisting of guanidine nitrate, triaminoguanidine nitrate, and mixtures of guanidine nitrate and triaminoguanidine nitrate.